Alpha blocker
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224001317
2008-07-06T22:03:14Z
SieBot
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robot Adding: [[he:חוסמי אלפא]]
'''Alpha blockers''' (also called alpha-adrenergic blocking agents) constitute a variety of drugs which block [[Adrenergic receptor#Alpha .CE.B1 receptors|α<sub>1</sub>-adrenergic receptors]] in [[arteries]] and [[smooth muscle]]s.
==Indications==
These drugs may be used to treat:
* [[benign prostatic hyperplasia]] (BPH)
**[[Lower urinary tract symptoms]]
**Post [[Transurethral microwave thermotherapy]] (TUMT) and [[Transurethral needle ablation of the prostate]] (TUNA) procedures
* [[high blood pressure]] (hypertension). This is not typically the drug of choice unless the patient also has BPH.
* [[symptoms]] of [http://health.yahoo.com/ency/healthwise/hw72762 non inflammatory chronic pelvic pain syndrome], a type of [[prostatitis]]. As a side effect they may reduce [[blood pressure]] and result in lightheadedness.
==Examples of alpha blockers==
Alpha blockers include:
* [[Doxazosin]] (Cardura)
* [[Prazosin]] (Minipress)
* [[Phenoxybenzamine]]
* [[Phentolamine]] (Regitine)
* [[Tamsulosin]] (Flomaxtra/Flomax)
* [[Alfuzosin]] (Uroxatral)
* [[Terazosin]] (Hytrin)
Tamsulosin is relatively selective for α<sub>1a</sub>-adrenergic receptors, which are mainly present in the [[prostate]]. Hence, it may have a more selective action in BPH with minimal effects on blood pressure.
==Adverse effects and interactions==
By reducing α<sub>1</sub>-adrenergic activity of the blood vessels, these drugs may cause [[hypotension]] (low blood pressure) and interrupt the [[baroreflex]] response. In doing so, they may cause dizziness, lightheadedness, or fainting when rising from a lying or sitting posture (known as [[orthostatic hypotension]] or postural hypotension). For this reason, it is generally recommended that alpha blockers should be taken at bedtime. Additionally, the risk of [[first dose phenomenon]] may be reduced by starting at a low dose and [[titrate|titrating]] upwards as needed.
Because these medications may cause orthostatic hypotension, as well as [[hypotension]] in general, these agents may [[drug interaction|interact]] with other medications that increase risk for [[hypotension]], such as other [[antihypertensive]]s and [[vasodilator]]s.
As discussed above, tamsulosin may have less risk for hypotension and orthostatic hypotension due to its selectivity for α<sub>1a</sub>-adrenergic receptors. On the other hand, the drug (a) elevates risk for floppy iris syndrome, and (b) might show ADRs characteristic of the [[sulfa]] related drugs.
==α<sub>2</sub>-blockers==
Although "alpha blocker" generally refers to α<sub>1</sub>-blockers, there are also α<sub>2</sub>-blockers, which are [[antagonists]] to the α<sub>2</sub> [[adrenergic receptor]]. Examples include [[yohimbine]], [[benzylpiperazine]], [[rauwolscine]] and [[idazoxan]].
==References==
* [http://www.drugdigest.org/DD/Comparison/NewComparison/0,10621,5-17,00.html DrugDigest] - Alpha blockers
* [http://www.rxlist.com/cgi/generic2/tamsul_cp.htm RxList.com] - Tamsulosin
* {{MeshName|alpha-Adrenergic+Blockers}}
[[Category:Alpha blockers|*]]
{{Antihypertensives_and_diuretics}}
{{Urologicals}}
{{Receptor agonists and antagonists}}
[[de:Alphablocker]]
[[es:Alfa bloqueante]]
[[fr:Alpha-bloquant]]
[[it:Alfa bloccante]]
[[he:חוסמי אלפא]]
[[ja:交感神経α受容体遮断薬]]